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    Power cord fuse for duet 2 wifi

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    • oliofundefined
      oliof
      last edited by

      3A at 240V is 720 Watts. The Duet 2 Wifi can take 24V at 15A (fuse limit), which is 360 Watts. So you are still at double the load the internal fuse would need to blow if you have a 3A fuse on your 240v side.

      See http://www.ohmslawcalculator.com/ohms-law-calculator.

      <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

      A Former User? 1 Reply Last reply Reply Quote 1
      • A Former User?
        A Former User @oliof
        last edited by

        @oliof sorry.. im not sure your meaning. So you mean 3A for 240V is still double the load?

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        • oliofundefined
          oliof
          last edited by oliof

          If you add a 3A fuse on the 240V side, it will trigger when the system behind that pulls 720 Watts. it will trigger when the input to the power supply exceeds 720 Watts.

          Since the duet Wifi's VIN fuse already triggers when the load is 360 Watts, (when run on 24V), this means the fuse on the 240V side will not trigger before the board fuse, but will give you protection in case there is a PSU failure (or the duet fails in a spectacular way making it's fuse ineffective).

          <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

          Danalundefined 1 Reply Last reply Reply Quote 0
          • Danalundefined
            Danal
            last edited by

            Again, fuses are about protecting wiring, not circuits or components. We've all drifted off into calculating the Duet, motor, heater total demand, or matching to the fuses on the Duet, or similar.

            It is true that the input side of the Power Supply needs to be LARGE enough to support the normal load with plenty of margin... and... perhaps equally importantly, or even more importantly, it really to be SMALL enough to protect the wire feeding the Power Supply (the cord).

            Therefore:

            • Assuming 18AWG input cord, no larger than 10A, to properly protect the wire.

            • Assuming a 240V 400W supply that is 80% efficient, no smaller than 2.08 amps.

            Given 'standard' fuse sizes, 3 or 5 would be fine 220V 400W.

            Delta / Kossel printer fanatic

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            • Danalundefined
              Danal
              last edited by Danal

              @daxzero Your various questions about "Why so Small" are all answered by the fundamental Ohm's Law that Volts * Amps = Watts. And Watts are the thing that runs motors and heaters and so forth.

              Therefore, if your printer is going to draw everything it can from a 400Watt supply, we find:

              • 400W / 220V = about 1.6 amps.

              Since power supplies are not perfectly efficient, we say the output may only be 80% of the input.

              • 1.6 / 0.8 = about 2 amps.

              That's why people are saying "3" and "5" and things like that.

              Delta / Kossel printer fanatic

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              • Danalundefined
                Danal @oliof
                last edited by

                @oliof said in Power cord fuse for duet 2 wifi:

                If you add a 3A fuse on the 240V side, it will trigger when the system behind that pulls 720 Watts.
                If you add a 3A fuse on the 240V side, it will trigger when the input to the power supply exceeds 720 Watts.

                Pedantic, I know... 🙂

                Delta / Kossel printer fanatic

                oliofundefined 1 Reply Last reply Reply Quote 1
                • A Former User?
                  A Former User
                  last edited by

                  if i using power supply 500W / 240V = about 2A, then i should used 3A for this... is that correct?

                  Danalundefined 1 Reply Last reply Reply Quote 0
                  • oliofundefined
                    oliof @Danal
                    last edited by

                    @Danal thanks for improving my description! We are talking electricity where I think pedantry is absolutely appropriate.

                    <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

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                    • Danalundefined
                      Danal @A Former User
                      last edited by

                      @daxzero said in Power cord fuse for duet 2 wifi:

                      if i using power supply 500W / 240V = about 2A, then i should used 3A for this... is that correct?

                      Yes, you want a little margin, and 3 is still well within protecting the wiring (10).

                      Delta / Kossel printer fanatic

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                      • DocTruckerundefined
                        DocTrucker
                        last edited by DocTrucker

                        You've not factored in the AC heater you want to use yet? That will be on top of the PSU requirement.

                        Don't forget if your PSU is 500W it will be consuming more like 625W on the mains side. Your AC heater will be added on top of the 625W.

                        Edit: Unless by 'power supply' you mean the total power consumption of your system...

                        Running 3 P3Steel with Duet 2. Duet 3 on the shelf looking for a suitable machine. One first generation Duet in a Logo/Turtle style robot!

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